Centrifugal fan



Aug. 11, 1936. H. F. HAGEN CENTRIFUGAL FAN Original Filed May 23, 1955 r N 0 W y a w w A w 6 W m J F 0 Q 9 w 3 w a Q a n W Q m m m W H QM m M7 I||| I i 1 1 a l I 1 I |L.-|||| Hm QM m 9w QM m QN 9 fla Patented Aug. 11, 1936 PATENT OFFICE? CENTRIFUGAL FAN Harold F. Hagen, Dedham, Mass., assignor to B. F. Sturtevant Company, Boston, Mass.

Original application May 23, 1935, Serial No. 22,979. Divided and this application March 14,

1936, Serial No. 68,846

2 Claims. (01. 230-114) This invention relates to centrifugal fans and relates more particularly to a fan, the volume of output of which and the driving horse power for which may be efliciently and satisfactorily adjusted without'adjustment of its speed of rotation.

This application is a division of my co-pending application Serial No. 22,979, filed May 23, 1935.

The motor most generally used for driving fans in power plants and other locations, is be- 7 cause of its efliciency and simplicity, an alternating current induction motor. The characteristics of this type of motor are such that it operates efficiently at a constant speed but the various expedients which have been suggested for varying its speed have not proved satisfactory. In power plants, for example, where fans are utilized for producing the forced draft required, it becomes necessary to vary the draft produced by the fan or fans, as the load on the plant or other conditions require it.

This invention provides a satisfactory control for the volume of output of the fan driven at constant speed for power plant and other purposes. This is accomplished by adjusting the spin velocity of the entering air at the inlet of the fan utilizing the ideas disclosed in my Patents No. 1,846,863, issued Feb. 23, 1932, and No. 1,989,413, issued Jan. 29, 1935. This invention is an improvement over that disclosed in my patents, in that a more eflicient fan with control mechanism is provided, the adjustment being substantially proportional to the volume of out- DU.

In my previous designs, a plurality of adjustable vanes were so placed in the converging inlet of a fan that they could be so adjusted from wide open position in which they had substantially no effect upon the movement of entering air,. through an adjustment of substantially 90 to a substantially, closed position where the entering air was given a spin approaching that of the fan wheel with the result the air was substantially not acted upon by the wheel and a greatly reduced delivery of the output of the fan was achieved. It was found necessary to place the vanes in a substantially conical shaped or converging inlet in order that propercontrol could be had. It was thought that it was required, in order that the control vanes should act effectively upon theair entering the inlet, that the outer portions of the vanes should substantially parallel and closely approach the walls of the inlet as shown by my said Patent No. 1,989,413.

According to this invention, there is provided an improved inlet passage and blade arrangement which results in greater efliciency, simpler construction and greater effectiveness of the inlet vanes. The inlet passage is formed as a continuation of the fan casing. It is shaped to form a Venturi passage, the inner portions of which form a shroud around curved inlet portions of the fan blades. The adjustable control vanes are mounted in the inlet passage substantially as shown by my said Patent No. 1,989,413 except that the inlet wall extends in a continuous convex curve towards the vanes and closely approaches the vanes at points of very limited areas, through which points the axes of the vanes extend. The wall is so curved that it is spaced a substantial distance from the vanes on the inlet side of their axes and converges rapidly towards and approaches closely the vanes at the points through which their axes extend, and then diverges rapidly away from the vanes.

An object of the invention isto provide an improved inlet arrangement for centrifugal fans.

Another object of the invention is to provide an improved inlet and blade arrangement for centrifugal fans.

Another object of the invention is to provide an improved inlet and control vane arrangement for centrifugal fans employing in the inlets, spin inducing vanes.

Other objects of the invention will be apparent from the following description taken together with the drawing.

The invention will now be described with reference to the drawing of which Fig. 1 is a side sectional view of a complete centrifugal fan according to this invention, and

Fig. 2 is a projected view of a preferred form of fan blade for use with the fan of Fig. 1.

The improved fan according to this invention is similar except for the fan inlet arrangement and the shape of the inlet portions of the blades to that disclosed in my Patent No. 1,989,413. The purpose of the present fan and its control vanes .is the same as that in my said patent so that it is only believed to be necessary to describe the improvement according to the present invention herein.

The fan wheel comprises the plurality of blades having the substantially fiat main working portions l3 and the curved inlet portions I2.

The curved portion l2 of each blade is formed I center line of the shaft 18, as shown more clearly by Fig. 2.

The curved inlet portions are recessed at their outer portions 8. The casing of the fan is formed at Hi to provide a stream-lined shroud extending within the recessed portions of the inlet portions l2 of the fan blades. The angle portions M are adapted for welding to the back plate I5 of the fan wheel.

The spin inducing vanes 2|, the inlet forming walls Land the inlet portions i2 of the fan blades are so arranged with respect to each other that the innermost portions of the vanes 2| terminate just short of the outermost portions of the fan blades; the axes I 9 of the vanes extend through the curved walls l at their points of nearest approach to the vanes 2|; the walls I!) curve in substantial curvature towards the vanes 2| on the inlet sides of the axes I9 and curve in substantial curvature away from the vanes'on the outlet sides of the axes, and the innermost portions of the walls form the stream-lined shrouds for the inlet portions l2 of the fan blades. This results in such a cooperative arrangement of fan inlet, vanes, and fan blades that the cost of construction due to its simplicity, is reduced and the more important fact that the efficiency of the fan and the efiectiveness of the control vanes are substantially increased over those of the prior arrangements.

The vanes 2| are adjusted by means of the gears 28 mounted on the inner pins 20. The gears 28 are rotated by the gears 29 which are mounted on the hub members 30 surrounding the shaft I8. The hub members 30 are rotated by the levers 3| which may be interconnected, in order that the vanes in both inlets of the fan may be adjusted simultaneously.

While the invention has been described in connection with a two inlet fan, obviously, the same principles apply to a single inlet fan. 5

While one or more embodiments of the invention have been described for the purposes of illustration, it should be understood that the invention is not limited to the exact arrangement described, since many departures may be made by those skilled in the art, after having had access to this disclosure.

What is claimed is:

1. A centrifugal fan comprising a fan wheel,. means forming an inlet passage into said wheel, a plurality of adjustable spin inducing vanes in said passage pivoted on axes which are oblique to the axis of said wheel, said passage being formed in a continuous convex curve extending in substantial curvature towards and in substantial curvature away from said vanes, the axes of said vanes extending through said curve at its points of nearest approach to said vanes.

2. A centrifugal fan comprising a fan wheel, means forming an inlet passage into said wheel, a plurality of adjustable spin inducing vanes in said passage pivoted on axes which are oblique to the axis of said wheel, said passage being formed in a continuous convex curve extending in substantial curvature towards and in substantial curvature away from said vanes, the axes of said vanes extending through said curve at its points of nearest approach to said vanes, at which points said passage closely approaches said vanes.

HAROLD F. HAGEN. 

